The sedimentary processes on tidal flats in the north of vietnam initial results and implication future proceedings of VAST

VIETNAM ACADEMY
OF SCIENCE AND TECHNOLOGY
(VAST)

~
Institut de recherche
pour Ie d'veloppement

INSTITUT DE RECHERCHE
POUR LE DEVELOPPEMENT
(IRD)xwvutsrqponmlkjih

ISBN: 978-604-913-162-2

BAo cso KHOA
HOC
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,,?
HOI
THAO VAST - IRD VE KHOA HOC
BIEN
•
•QPONMLKJIHGFEDCBA
,,?

P R O C E E D IN G S O F
V A S T - IR D S Y M P O S IU M O N M A R IN E S C IE N C E
H a ip h o n g - V ie tn a m , N o v e m b e r

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28th_29th, 2 0 1 3

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N H A X U A T B A N K H O A H Q C T V N H IE N V A C O N G N G H I;


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Levels of heavy metals in muscles with relation to the growth
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Macrobenthic communities in estuarine mangrove ecosystems subject to
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164

The sedimentary processes on tidal flats in the north of Vietnam: initial results
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164

BAo cAo KHOA HOC HOI THAo VAST - IRD V~ KHOA HOC BI~Nxwvutsr

THE SEDIMENTARY PROCESSES ON TIDAL FLATS IN THE
NORTH OF VIETNAM: INITIAL RESULTS AND IMPLICATION
FUTURE

Nguyen Thi Kim Anh', Nguyen Mai Luu', Nguyen Dinh Khang 1

Phan Son Hae, Nguyen Manh Ha\ Ph am Tien Due", Lai Thi Bieh Thuy4 NMLKJIHGF
1

In
dcbaZYXWVUTSRQPONMLKJIHGFEDCBA
s titu te o f M a r in e E n v ir o n m e n t a n d R e s o u r c e s ,

V ie tn a m A c a d e m y

o f S c ie n c e a n d T e c h n o lo g y

(V A S T )
2 N u c le a r R e s e a r c h In s titu te , D a L a t
3

F a c u lty o f C h e m is tr y , H a n o i U n iv e r s ity o f S c ie n c e s

" C e n tr e fo r G e o lo g ic a l A n a ly s is L a b o r a to r y ,

H a N oi

1. SUMMARY
Tidal flats in North Vietnam extending from Mong Cai (Quang Ninh province) to
Kim Son (Ninh Binh province) are affected by human activities and land - ocean
interaction processes. It can be shown in erosion, accretion, accumulation of pollutants
with time. For understanding sedimentary processes on tidal flats, samples from 11
collected sediment cores were in analysis of 210Pb, 226Ra, grain size, metals and

minerals. The sediment parameters on tidal flats are divided in three sedimentary
environment types, including Deltaic tidal flat sedimentary environment from southwest
Do Son Peninsula to Kim Son and dominated by accretion processes, estuarine tidal flat
sedimentary environment from northeast of Do Son Peninsula to southwest of Cat Ba
Islands, and embayment tidal flat sedimentary environment from Cat Ba Islands to
Mong Cai and characterised with slow accretion and small rate of sedimentation.
K eyw ords:

tid a l fla t, s e d im e n ta r y p r o c e s s , N o r th V ie tn a m ,

21O p b ,

h e a v y m e ta ls .

2. INTRODUCTION
Tidal flat which is a kind of coastal wetlands plays an important role for human
life by providing space for socio-economic development and being in high biodiversity
[20]. Because the tidal sediments record many of information on the impacts from
nature and human activities, it is a key factor to understand sedimentary processes.
Tracking environmental changes using many indicators of biology and geochemistry
[12] can help us to get information on environment conditions in the past and at present.
The coastal provinces of North Vietnam extend from Quang Ninh to Ninh Binh
where the rivers discharge to sea through their mouths of Ka Long, Tien Yen, Ba Che,
Troi, Bach Dang, Carn, Lach Tray, Van Uc, Thai Binh, Ba Lat, Ninh Co and Day
(Fig. 1). The channels which bring water from mainland to sea are changing coastal


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environment conditions. The coastal environments record human impacts, nature events
in sediments, but they are reflected changing with time.
As part of the coastal region of North Vietnam, intertidal zones interest many
scientists, indicating with the number of articles on environmental sediment. These
studies can help us understand environmental conditions as sedimentation and erosion
rates [11, 15, 19,21], geological structure of tidal flats in Holocene [7, 18], sediment
compositions [9, 16] and sediment geochemistry [1, 2, 6, 14, 19]. These publications
have shown that nature and human activities are influenced on the tidal environment.
Our research questions are in the past and at present what the human and the
nature have affected on the tidal environment. By analysis of sediment cores in the tidal
. gram
.. size, 210P b , 226R a, meta Is an d mmera
mi
1s, se diirnentary processes on tiid a 1 fl ats
fl ats m
will be clearer understood.

3. MATERIALS

AND METHODS

3.1.dcbaZYXWVUTSRQPONMLKJIHGFEDCBA
M a te r ia ls

During 2009 - 2012, three campaigns were carried out to collect samples of sediment

cores Me 6 (0-40cm) and Me 5 (0-63cm) in April 2009, Me 8 (0-40cm) and Me 11(050cm) in October 2010, and Me 1(0-90cm), Me 2 (0-70cm), Me 3 (0-70cm), Me 4 (090cm), Me 7 (0-90cm), Me 9 (0-90cm) and Me 10 (0-90cm) in March 2012 (Fig.1).

21'
34'

106· 00'

--

108001'

I

~

(

,<

~ "l' NMLKJIHGFEDCBA
J

-

'%( •

p

f

'"

'.~

VTNHBACB<)

LEGEND
•

COle positions

,
,,+.
s

19.~.>."

55'~

.'

19
•
55'

108001'

106· ~O'

Fig. 1. Position

1

1

of sediment

cores on the tidal flats of North Vietnam


BAo cAo KHOA HOC HOI THAo VAST - IRD ~
166xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

3 .2 .

KHOA HOC BI~NdcbaZY

Methods

We had cut 2.0 em per samples from the top to the end of cores, and kept them at
4°C in field before storing in laboratory. In the laboratory, all sediments are dried in aircondition at 16°C.
Grain sizes of sediment were analyzed by sieves for coarse grain (> 0.063mm) and
particle size analyzers CILAS 990 for fine grain « 0.063mm) after removing salts and
organic matters by distilled water and hydrogen peroxide (10% H 202). Sediment
classification is according to Lisitzin [13].
The 2lOPb analysis in sediments was calculated indirectly by 2lOpO in sediments,
the sediments were extracted by HN03 and HF concentrated. Then we used 0.1 %
diethylammonium diethyldithiocarbamate and chloroform in 5M HCI to absorb 210pO
by silver dish and measured on alpha s£ectrometry. We used 209pO as initial standard
assess recovery of extraction [8]. The 22 Ra in sediments as background were measured

directly by gamma spectrometry. The constant rate supply (CRS) model is used to
calculate chronology
of sediment layers (1). This model was suggested by
Krishnaswami [10], later have been modified [3, 4, 17]. Nowadays, this CRS model is
used very common in calculating sedimentation rate in coastal and estuaries.
(1)
Where t: year;

A constant = 0.031;
A(O) is total of 210Pbexcess
in sediment core elOPbcxccss=210Pbactivity
- 226Ra);
A(x) is 210Pbexcess
in sediment core at depth x.
For metals analysis: Weighed 0.5g dry sediments, then were extracted by 10 ml
8N HN03 and 3ml 30% H 202 under reflux column at 95°C in 15 minutes. After that
samples were cooled and added about 5ml 16N HN03, then kept at 95°C in 2 hours
(Method 3050b), cooled and filtered by 0.45 urn papers (Whatman). Finally, samples
were diluted to 100 ml and measured by using ICP-MS method (Elan 9000 Perkin
Elmer). All chemicals are in grade analysis. For control Q A lQ C of analysis processes,
the certified reference material samples (PACS2, MESS-3) were used.
Minerals in sediments were analyzed by two methods, which were analysis by
thermo gravimetric on STA-PT 1600 instrument for clay minerals with relative error ±
5%; other minerals were analysis by X-ray diffraction analysis on D8-Advance Bruker
instrument with in ± 3% relative error.

4. RESULTS AND DISCUSSION
4.1. Distribution of grain

s iz e

in tidal flats

From Mong Cai to Kim Son, sediments on tidal flats were composed of coarse
sand (Md = 0.50-1.00mm), medium sand (Md = 0.25 - 0.50mm), fine sand (Md = 0.10 0.25mm), coarse aleurites (Md = 0.05 - 0.10mm), fine-aleurites muds (Md = 0.01-


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0.05mm) and alerutic-pelitic muds (Md < 0.05mm). Coarse, medium and fine sands
were only in the north of the study area (MC 1, MC 3) and most of them were medium
and well in sorting. Fine-grain sediments dominated the south of the area and most of
them were poor to medium in sorting.
In Fig. 2, the diameters of sediments in the cores changed in depths, reflecting the
change of sedimentary environmental conditions with time. Based on the diameters,
sediments can be divided into two sedimentary processes of erosion and accretion on the
tidal flats. Erosion processes are seen at MC II in depth of 27-50 em. At MC 10 erosion
and accretion were alternative from 22 to 90 cm, at MC 8 in depth of 33 - 40 em, at MC
3 in depth of 20 - 66 em and on MC I at 15 - 90 cm, where the diameters were from
coarse aleurites to coarse sands. Accretion processes are seen in all cores, at MC 11 in
depth of 0-27 cm, at MC 10 from 0-22 em, at MC 8 in depth ofO-27cm, at MC 7, MC 5
and MC 4 in all of dep,th in cores, on MC I and MC 3 in depth of 0-20cm.
Based on mean diameters (Md) of sediments, three areas were divided, including
Deltaic tidal flat sedimentary environment (MC 11, MC 10, MC 9, MC 8, MC 7) with
most sediments of coarse aleurites to fine-aleurites muds; Estuarine tidal flat

sedimentary environment dominated by fine-aleurites muds (MC 4, MC 5); and .
Embayment tidal flat sedimentary environment dominated by fine to coarse sands (MC
1, MC 3).
Table 1. Sediment parameters on the tidal flats
SoNMLKJIHGFEDCBA

M d (mm)
CoresQPONMLKJIHGFEDCBA

SO .
M in .
dcbaZYXWVUTSRQPONMLKJIHGFEDCBA
M ax.
A v e r.

SO .

M in .

M ax.

A v e r.

MC1

0.052

0.725

0.224

0.119

1.297

6.381

2.280

1.497

MC3

0.080

0.181

0.130

0.021

1.531

4.047

1.887

0.654

MC4

0.008

0.057

0.024

0.015

2.284

3.988

3.262

0.380

MC5

0.008

0.034

0.015

0.007

1.601

2.986

2.686

0.324

MC7

0.022

0.063

0.048

0.012

1.740

3.557

2.991

0.408

MC8

0.019

0.116

0.040

0.029

1.803

3.060

2.565

0.255

MC9

0.054

0.102

0.065

0.008

1.255

3.635

2.119

0.810

MC10

0.051

0.084

0.066

0.007

1.233

3.588

2.108

0.848

MC 11

0.037

0.068

0.057

0.008

1.366

2.696

2.151

0.410

Min. = minimum; Max. = maximum; Aver. = average; SD. = Standard deviation


BAo cAo KHOA HOC HOI THAo VAST - IRD V~
168xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

Sediment

QPONMLKJIHGFEDCBA
SJ
pw am e

•••.•

(Md,

KHOA HOC BI~N

J M II'W 'I8 1 e r1 (Md,

Sedment

Sol

...,

Me.

Sediment

paramelera

(Md,

Sediment parameters

so>

{Md.

SJ

__

lAd("",,)

-.-

S.

Sedimentary

MC8
___

parameters

/

(Md,

so>

NMLKJIHGFEDCBA
'\lT i'
' ,

",(mm)

~s.

-.,
,,/

./
Sediment

paramelltf$

(Md,

so>

Sediment

Fig. 2. Distribution

4 .2 . D is tr ib u tio n

O f2 1 O

Pb and

parameter

(Md,

so>

Sediment

parame\efl

(Md.

SJ

of sediment parameters on tidal flatsdcbaZYXWVUTSRQPONML

226 R a

a n d s e d im e n ta tio n

r a te o n tid a l fla ts

The 210Pb and 226Ra in sediments can help us tracking change of environments;
they are indicators for erosion or accretion processes. When the content of 226Ra in
sediment layer is higher than that of 210Pb, there is no deposition of sediment. On the
other hand, if the content of 210Pbin sediment is higher than that of 226Ra, it will show
the deposition of sediment. On the tidal flats of North Vietnam, there are consisted of
two above cases.
In the sediment cores Me 2, Me 4, Me 5, Me 6, Me 7 on the tidal flats, the
content of 210Pbactivity
is higher than that of 226Rain a111ayers, indicating the accretion in
these areas for the whole time (Fig. 3). In the sediment cores Me 3, Me 8, Me 9, Me
10, Me 11 in the tidal flats, there are in these sediment cores two phases, including the
first phase with content of 210Pbactivity
in sediment higher than that of 226Raand the later
second phase with content of 226Rain sediment higher than that of 210Pbactivity
(Fig. 3).


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.., ..,

J"Pb_

,

'1

.. ,..,

and lltIRa (8qlkg)

.. ..,

11OPb_

,

,

"

""

J

·
I~j ,t
•·
;

,

..

-+-"'"PD_

~~

f

,

toe

"

'~

c:

Me2

.. ,..,

and mRa (SqIIotg)

'"
"
· dcbaZYXWVUTSRQPONMLKJIHGFEDCBA
.rr>

"

169xwvutsrqponmlk

ON MARINE SCIENCE

,,

'"

,,
"I

Me3

1:1NMLKJIHGFEDCBA
f

.'I ••

1:1

-+-

210

...•..

22&Ra

PblldMly

.. ..

J~_.nd~(8q/IIgl

"

I

"

)

'>

"

'"

'"

Me4

_210PII~
..".22eRlt

!"

I

t

•

.. .. .. ~""
210P!:l_

,

:1

:1

/

t

"

and mRa (8q/tg)

'~==

:j
~"
.'I ••
"
"ss
""J

,

:1

"

"1

~-..

.. ,..,

and Z2tRa(Bqlkgl

roc

"

r-

~

,

'"

<

{

K"i "
o as

_"'Pb-,.

.. ..

2· 'Pb....,

..

,

M'-'

X

I

'"

..,

t

MC6

__

:,

"

"

"

'"

'"
Me,

c

..

'>OPb_

~~

..

J"'AI_ and -Ra (8qI\g)

,

---'~~~ ..

~

5 ••

!"

.. '

,

:1

..

",

710

Pb.....,

't'

1i

and mRa (Bqlkg)

"

'",

'I"

..,,

.. ..

:h0P!)_

•.

, ,
" "

,,

and 21IIRa

"

'"

'"

Me.
-v-

:1 j)

'''Re

I"

j"

"

t ••

,,

.. ..

'''Pb_and~'

"

b

"j

"
"

....•... ''''PtJ..-,.

..

,

"

~g)

,.,

".
Me 10

MC9

~

__

210~

I ..
j

- •••-

226R•

!"

P

-""""~ ..•.

l"Pb_ and 22IRa(BqIkg)

o
01

_

_
•••

1

_

_

._

I

I

._

._

._
1

Men

~-..
__

K"

'''Pb_

t"

.'I "

as

,,'

Fig. 3. Distribution of

210Pb

and

226Ra

in sediments on tidal flats

Sedimentation rates on tidal flats were timely changed in different areas. They
were low in Me 3 and Me 10 (Fig. 4), high in Me 2, Me 4, Me 5, Me7, Me 9, Me II
(Table 2 and Fig. 4). On tidal flats, there were not only accretions, but also erosion that
was indicated at Me II, MetO, Me 9, and Me 8. The sedimentation rate is closely
related to the diameter of sediment. The high sedimentation rate, the much more fine


BAo cAo KHOA HOC HOI THAo VAST
170xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

- IRD V~ KHOA HOC BI~N

sediment is. In three sedimentary environments mentioned above, high sedimentation

rate was recorded in estuarine tidal flat sedimentary environment and deltaic tidal flat
sedimentary environment.
Table 2. Sedimentation rates (em/year) on tidal flatsNMLKJIHGFEDCBA
M C2

M C3

M C4

Max.

0.11
1.31

0.04
0.34

0.19
2.35

A v e r.

0 .8 2

0 .1 4

1 .4 0

SD.

0.37

0.11

0.65

Min.

Min.

=

minimum;

M C5

0.13

15.00
2.94
4.01

=

Max.

M C7

M C6

0.26

M C8

0.17
14.42

1.18

M C9

0.07
3.24

MC

MC 11

10

0.06
15.83

0.14

0.09
14.84

0.64

0 .5 0

2 .0 8

0 .7 7

3 .0 4

0 .3 4

1.71

0.31

3.105

0.83

5.27

0.15

4.15

= average;

maximum; Aver.

SD.

= Standard

deviation

In Table 2, at MC 5, MC 7, MC 9 and M C II standard deviation of sedimentation
rates are high, because in these cores sedimentation rates are change very fast and
suddenly (Fig. 4), they show that effect from sedimentary environment, we are also
seeing same trend changes by concentration of metals and clay minerals and quartz in
these sediment cores.

.

Sedimentalioo

rate

.

(anlyear)

Sedimentation

rates

(cmlyear)

""
"'"

"",,,.

...•
""
....
.......
,
....
....
...,

'9111

MC 2

"51

MC3

""
-"""
~

..

'"3

,

"..

:"":::

"""
,, ,

..

..."
....
"..

117.

,...

> .,

1'13

.•.

,

""
,."

.

Sedimentation

...

1911
'1173

,

''''

""

.

rate (cmfyear)

•••~~->--~->---+--->---+-----<

Me5

!!

e " ••

..

19845

1981

"

,...
,
""

1'70

""
""
""

•..

,

1.71

""
""

....

1'15

...

,

1912

'&71

rate

"

= ••••

>

55

""
"
""

..

Sedimentation

(cnVyear)

rate

(cm'yeat)

~H'~~~-~"",;,,-+-~->--~

...,
""
""

MC.

I :~ l
G

""
,"
"

..
..
''''

f g
dcbaZYXWVUTSRQPONMLKJIHGFEDCBA

'.1 0

199&

'995

'970

Sedimenlalion

""
"'":::
...,

,

::

.
""t====~=====:;:;;;-:::

Mea

Me7

·...

>-

..

rate (anlyear)

(emlyear)

..
~r---;=====~======-....
...,

"
Sedimentation

rates

""
"""
MC6

1911

""

Sedimentation

"" r-""t"""->--~--~->---+-----<

19711

1111'

...
,"-...
,.

.

(cm'year)

11191

:

>-

1'71

"",
K'IM

Sedimentation rate

""~~->---+--->---+--~>---+-----<

"'"
..
"",."
.
""
,...
",.. r~:::;~~~=====-""
~ ,,....,,

""""
"
""
,
""

MC.

· .....

rt

i~
!"
.,.
; ..

I "••

~

rate

::~r---j.-+-.....;..-+--+--+-~--<

e ,",

S

Sedimentalion

"" ~~-+--+-+--+--+--+---<

""
""
""
""''''

>-

.

(cmtyear)

,,,,t-"r--->--~->---+---':'-~---<

__

"79
Hil"

1 .7 0

1 !:!

l5

·

~ S"

::
""
""
"

MC10


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Sedm.ntalion

rate

ON MARINE SCIENCExwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHG
171

(O'I'IIyNr)

Me 11

rates on tidal flatsdcbaZYXWVUTSRQPONMLKJIHGFEDCB

Fig. 4. Sedimentation

4 .3 . D is tr ib u tio n

o f m e ta ls o n tid a l fla ts

Heavy metals in sediment cores were analyzed including Cu, Pb, Zn, As, Ni, Cr.
High concentrations of elements are As, Cu, Pb and Zn in MC 5, MC 6, M NMLKJIHGFEDCBA
C 7 , MC 8
and MC 10. In comparison with MC 1, MC 2 and MC 3 in the north of the study area,
the concentrations of metals in the south of the study area is higher. Metals in sediment
cores increased in recent years, clearly in MC 5, MC 8 and MC 2 (Table 3).
Copper (Cu) in sediments were in the range from low to high concentration, the
highest concentration at MC 5 and MC 6. Most of them are higher than ISQG levels of
Canadian standard. The lower concentration compared with ISQG is in MC 1 MC 2 and

MC 3 (Table 3).
The concentration of lead (Pb) in sediment had a trend similar to the one of Cu. It
was high in sediment cores MC 5, MC 6, MC 7, MC 8 and MC 10, only at MC 1, MC 2
and MC 3 but lower than ISQG level. The highest concentration was at MC 7.
Table 3. Value of metals (mg/kg) in core sediments on tidal flats
M C1
M e ta l

(n =

Cu

M C2

M C3

M C5

8)

(n = 2 0 )

(n = 2 1

)

(n =

24)

M C7
(n =

23)

M C8

M C10

(n = 1 7 )

(n = 4 )

M C

11

(n = 1 8

Min.

2.17

10.06

0.69

47.66

53.25

60.31

19.93

33.68

11.42

7.37

18.84

12.14

70.88

89.01

94.76

85.59

74.55

36.12

A v e r.

5.12

1 4 .8 0

3.85

57.58

8 0 .0 5

72.93

5 6 .0 3

5 0 .4 1

23.72

SO.

1.83

2.20

2.80

8.03

8.46

7.78

21.51

17.54

6.77

)

18.70

Min.

5.78

18.37

5.99

59.61

55.36

70.96

22.32

60.59

12.67

Max.

26.06

31.12

22.99

90.20

82.25

120.32

96.28

103.01

111.63

A v e r.

19.59

23.71

12.69

76.16

72.25

95.02

61.27

79.41

28.61

SO.

6.98

2.93

4.00

6.88

8.72

12.24

22.48

18.76

21.43

Min.

3.95

13.26

19.63

87.46

94.25

72.21

62.19

88.60

26.67

Max.

45.66

492.01

62.64

137.68

132.99

143.68

151.79

152.08

152.16

A v e r.

30.69

81.62

35.89

111.66

123.05

98.89

1 0 6 .2 2

113.80

65.97

SO.

14.39

111.89

11.37

18.26

8.72

17.71

27.20

30.93

29.88

30.20

ISOG
Zn

(n = 1 9 )

Max.

ISOG

Pb

M C6

L e v e ls


BAo cAo KHOA HOC HOI THAo VAST
172xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

- IRO V~ KHOA HOC BIf:N

124.00

ISQG
Min.

0.61

3.15

0.26

23.43

20.24

25.78

7.13

13.27

376

Max.

6.69

9.69

8.41

53.93

42.94

38.62

42.16

30.81

12.09

AsNMLKJIHGFEDCBA
27.53
A v e r.

4.22 dcbaZYXWVUTSRQPONMLKJIHGFEDCBA
6 .1 0
3 2 .8 0
38.29
4 .0 1

26.68

21.66

7.31

11.38

7.96

2.22

2.18

SO.

2.21

2.18

5.27

12.86

Ni

Min.

10.88

9.93

2.60

30.96

23.16

34.66

8.74

34.88

2.05

Max.

23.86

41.44

24.97

44.80

36.83

74.11

63.67

55.97

323.32

A v e r.

16.38

18.12

1 6 .0 9

3 8 .1 0

31.92

44.18

32.41

44.49

45.89

4.18

8.43

6.62

4.34

3.85

9.82

12.01

8.75

83.66

SO.

-

ISQG

Cr

4.00

7.20

ISQG

Min.

5.35

17.07

5.98

34.40

28.71

32.35

12.70

30.67

8.86

Max.

22.17

54.46

17.65

49.80

47.83

53.33

50.83

44.40

22.71

A v e r.

16.44

24.11

11.47

41.98

41.41

4 2 .6 0

33.19

36.55

15.78

ISQG

5.74

8.30

2.75

5.11

4.39

5.00

12.75

5.79

3.53

52.30

TEL

Min. = minimum; Max. = maximum; Aver. = average; SD. = Standard deviation; n= number of sample

Zinc (Zn) has high concentration in sediment
Although average concentration of Zn was lower than
were higher than ISQG level. At some positions on
recently (Me 8, Me 11, Me 3 and Me 2) increased.
Me 1 and Me 3 (Fig. 5, Table 3).
Concentration

of metals

(mgIkg

dry weight)

Concentration

of metals

eo

80

(mgfkg

in Me 5, Me 6 and Me 10.
ISQG level, some layers in cores
the tidal flats, the concentration
The lowest concentration was in

dry weight)

JOe)

of

Concentration
500

~r.~--~7/,'~'--------'

0102030

40

50

60

metals
7011090

(mglkg dry

weigl!)

100110120130140150160

o~~~~~~~~~~~
MC3

"

MC1

~""
...••.•

Pb

MC2

..• -. In

Concentration

of metals

(mglkg city

weight)

Concenltalion

of metals

(mglkg

dry weighl)

Concentration

of metals

(mglkg

dry weight)


PROCEEDINGS

Concentration

o

~u
~c"

•.•..

Concentration

dry weight)

(mglkg

o I

40

of metals

60

"

'"

.:::.:

20

•..........•........

Concentration

'''''
.....
1

-"

I~

,_

"',

•••••
. e-

"w

dl)' weignt)

•

<,

Me11

,.~~,(

K"

(m~g

o 10M..

"'--"

,+

//

Pb
Zn

", ..
L
dcbaZYXWVUTSRQPONMLKJIHGFEDCBA

Fig. 5. Distribution

of metals

1~

.•

~c..

rJ

c-,

120

.,>

,.

•...

':;::::~;:a

dry weight)

100

....tn. ...'!

,':0

Zn

(mglkg

80

=-L..

~~~.~'.

Pb

.--

K

of metals

20

~

173

ON MARINE SCIENCE

xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
o
~

_
~
~
,~
o
NMLKJIHGFEDCBA
vv:==::; m:: '.~~:~:~_~~~'.
'1-

Mca

01

1

OF VAST - IRD SYMPOSIUM

~

.0

£
~

so

o

/
..,/

W'

Me 10

.

~""
~• "'0

of Cu, Pb and Zn in sediments

on tidal flats

Arsenic (As) in sediments was quite high in concentration, up to five times higher
ISQL levels. Arsenic at Me 1, Me 2 and Me 3 had concentrations lower than ISQG
levels.
Concentration

of metals

(mQlkg

Concentration

dry weigh!)

of metals

(mglkg

dry weight)

Concentration

of metals

(mg.l\.g

dry weight)

..•.......-- ...--\-~::::.::::~-::::::=-.,.
.~.!'
•.. _

~.=:;::.~-.

-''P-~

MC1

~"
__

K"

e-:"

Hi

K
~

~'"

£

__

£

~"

Pi

,,-.--' .-

\
•

"

.•.

,

..

~

,

_ ••••

MC2

~,.

N,

•

MC3

..·•. ··N'
•
C,

C,

...
! .
,J

o

•

!

Concentration

o

H'

01

I

~u

off metals

(mglkg

~u

""

~u

MC5

o

''''

10

N!

of metats
~

••

(mglkg

•

.•••••

dry weight)

~

Concenlration

~

_

o

I

B

01

IV

LV

I

.

K

;;"

~JB

Concentration
10

20

K

1

g ...

C,

UU

Iv

DO.

~,.
·-•.··N'
'"

.,)'!, .
'<;.,"'".
~ ,"

K"

~"
i
0"

..••...

(mglkg

.0
so
::=;l;:w:
.....
)e

Concentration

dry weight)
60

o

._

I

o

50

100

of metals
1~

(mglkg
200

Concentration

dry weight)
250

300

o

."

lV

~

of metals
.JU

4V

(mg/kg
~

dry we.ght)
O\J

ru

II

Or'---+-.r+--~,.-hr-~--~--+-~

Iwq

Me 10

'---

'.

H;

dry weight)

MC 7

•...

!

,.'.

Mca
__
~A.

01 metals
30

""

-::;:-.-

NI

? ~)
o
I

(mg/IIg

~V

Wi

MC6

~,.
'"

.

-
o

of metals
.••••

•

•..~~;;~---==-~=:!:~.

--~

• -- 0

~

o I

•..: I e

~,"~,,""
•.•.•

Concentration

dry weight)

IJI'

: J iiU

..~

MC

~"
~.

-=--==::=:--.-

~A.

1'~ ..

· .• · · Cr

~N'
~C,

1..
0

'I."

20

.

... ;.-....

)i

-

~"

,
~----..•....----.-

~~~

__ -:':=;"~

~

"

--._.,.
Fig. 6. Distribution

of As, Ni and Cr in sediments

on tidal flats

/


174xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
BAo cAo KHOA HOC HOI THAo VAST

- IRD V~ KHOA HOC BI~N

Niken (Ni) in sediment got its high concentration at MC 7, MCI 0 and MC 11, but
low concentration at MC I, MC 2 and MC 3. The increasing in concentration ofNi was
shown at MC I, MC 2, MC 3 and MC 8 (Fig. 6).
Chromium (Cr) in sediment on all tidal flats had its concentration lower than
ISQG level, changing in a sediment core but not clear among the cores. The highest
concentration of Cr was recorded at MC 5, MC 6 and MC 7.

Along tidal flats of the North Vietnam, heavy metals are high concentration of Cu,
Pb, As and Zn, most of them is higher than ISQG levels. High concentrations of metals
are focus on Hai Phong to Ninh Binh coastal area, where mean diameters of sediment
are smaller and clay minerals content are higher than Cua Luc to Mong Cai.dcbaZYXWVUTSRQPO
4 .4 . D is tr ib u tio n

o f m in e r a ls

o n tid a l fla ts

Minerals in sediments on tidal flats are monmoriolite, kaolinite, illite, chlorite,
fenspate, quartz and goethite. Clay minerals which are common in sediment cores are
kaolinite, illite; monmoriolite and chlorite had low concentrations (Fig.7). Quartz was
high in concentration in all the cores while other minerals (fenspate and goethite) were
low in concentration in tidal sediment (Fig. 8).
Monmoliolite was not common in tidal sediments of North Vietnam, its
concentration was highest in MC 5 and MC 6. There was no change or less than limit
detection of equipment at MC 2, MC 3.
Table 4. Value of minerals (%) in core sediments on tidal flatsNMLKJIHGFEDCBA
M C2
M in e r a l

(n =

~

M C3

M C5

M C6

M C7

20)

(n = 2 1

)

(n = 1 6

)

(n =

14)

(n = 2 3 )

Min.

3.00

3.00

3.00

3.00

3.00

"§

Max.

3.00

3.00

E

A v e r.

3 .0 0

3 .0 0

6.00
4.44

0.00
11.00
18.00
15.45

4.00
15.00
7.67

1.26
14.00
23.00
19.13

6.00
4.43

1.40
15.00
23.00
19.79

5.00
3.22
0.60
8.00
16.00
12.26

Max.

1.70
10.00
19.00

3.06
7.00
19.00

3.12
21.00
27.00

2.58
16.00
29.00

A v e r.

0

c:

~
2

SO.
Min.

:S

Max.

0
co
::.:::

A v e r.

2

·c
0

z
(J
OJ

roa.
'"

c
OJ

u.

~
~

M C

11

0.00

(n =

16)

3.00
4.00
3.19
0.40
7.00
13.00

(n = 2 0 )

3.00
5.00
3.45
0.61
6.00
14.00

1 0 .3 1

9 .1 0

1.89
17.00
29.00

2.15
15.00
25.00

23.56

1 9 .7 0

3.60

3.10

1 5 .9 0

12.76

2 4 .0 0

2 4 .0 0

2.20
19.00
27.00
22.65

SO.

1.77

3.94

2.16

3.11

2.55

Min.

5.00

8.00
11.00

6.00
10.00

7.00

6.00

6.00

3.00
7.00

5.00

Max.
A v e r.

5 .2 0

4.68

8.94

8.43

7.00
6.65

10.00
8.13

9.00
6.95

SO.

0.41

1.65

1.00

1.59

0.57

1.09

Min.

3.00

3.00

5.00

4.00

4.00

5.00

0.83
4.00

Max.

5.00

6.00

15.00

13.00

14.00

4 .4 0

4.00
3.14

7.00

A v e r.

5.88

SO.

1.42

6.69
2.70

2.82

39.00
63.00

0.96
20.00
39.00

6.74
2.77

Min.

0.81
48.00

5.29
0.73
22.00
47.00

31.00
47.00

32.00

SO.
Min.

~

M C8

L e v e ls

Max.

83.00

52.00

7 .2 0

38.00
59.50


PROCEEDINGS

SD.

46.15
4.92

Min.

6.00

Max.

8 .0 0

A v e r.

7.35
0.75

A v e r.

2
:.c
Q3
0
(9

ON MARINE SCIENCExwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIH
175NMLKJIHGF

OF VAST - IRD SYMPOSIUM

SD.

64.76
8.89

3.00

27.56
4.07

6.00
4.33
1.56

9.00
6.56
1.26

29.43 dcbaZYXWVUTSRQPONMLKJIHGFEDCBA
3 9 .3 0
39.31
4 6 .3 0
5.96
5.00
8.00
6.57
0.76

5.00

4.58
4.00
7.00
5.65
0.83

6.11
4.00
7.00

4.79
3.00
7.00

5.88
0.89

5 .1 0

0.79

Min. = minimum; Max. = maximum; Aver. = average; SD. = Standard deviation; n= number of sample

Kaolinite had a high concentration after those of illite and quartz. The highest
content was at Me 2, Me 5 and Me 6; the lowest content was at Me 3 and Me 11.
Taking kaolinite as an indicator for accretion, it shows accretion in all depth of the cores
Me 2, Me 5, Me 6 and Me 7.
Illite had the highest concentration in clay minerals of tidal sediments and been
observed of changing as of kaolinite. It is a good indicator for understanding
environmental conditions; at position of cores have high sedimentation rate which are
positive linear with content of illite.
Content

o

i ••

:
i

l

~

sr
~_o

i

f~ ;,

::a

,

)

ov'"

•.•.~

25

f

)

..

Hlil.
C\of~.

,"

s

ro
I

~"1
5 "

'.

9

/'

~.W

~"

KaoIln~e
a Illite
~<>-- Clorlt8

o
. •..

)

Q

•

of minerals

of minerals

I

~.,.
'

I
, ...

..

~.
~ .
-.

,.

eo

B

(%)

Conlent
25
I

'.

~

,

_.~.;:.o
•
Q

Q

..•.

'.

,

01 minerals

Me7
__
.,.

••

.oo

l
~ zc
5

!

...• -.

~~.'
-;:::=-.
~,Y)

Monmoriol~.

•
iii.
· · <>· · · CIort.

(%)

o

o

~" ~

.

·:i
0'

as

"

·
. ··. .

,.

b

..

lUte
CIof.,'4;<

"

"

e-;

0

0

I

• .•

-:-:~."'

~
0"

••••

p

~

II

••

Conloot

o

°1

.

."
•.

~.

/

~

MonrnonoI~e

.-

Q~t

.. " ....•• a

1.

ro1

..

"'~

c

"

(%)

.;~Iwn

.",

9 ~

I 9~"::····..,:
I, • " :::
!", I

'
.P-'"· 'I

.)

I

" , 't . " . '

A

~ ~ ·.~ i
-+-

o

•

Content

0

K.omH

'.

I>

'I

.i

,,:, ......•

,.

.

i ~ ..

•..

r:'::~:f;

.: '," .: : : .: : -

+


•

(%)

,.9'

_ _ MorImoIioI~.
.••
I

I

•

40

'1.
'I ..

q;

~

1

I

MC6

,·-1

. ..:~ •

D'

3D

~_

:

.>

%'"
~

of minerals

e,

~)

. i

~ ..~.~Q' .."
~

o

••

: r

I

0 : ·~ : b

0:::.

I t:
•

.w

(I~'.

I

r-.·.·.·~...

_~~D

Content

o

t

I

v.

;

,

I

.A r

Monmoloit.
Kaolin~ãã
!lit.
CIor~.

Conlent 01 minerals

(%)

o

Me2
ã.ã.ã
'1
I:t
.- ..

,.

,

01

15

,

ã~ -.ã
i

Vi
o

"

,

,

_1_

s-,

'>

,.

f

..

Content 01 minerals

(%)

~v

0,,,0.._

.."

j

1"

of minerals
.~

Mea'

.-"

ô

f .i.
"

,

-<>-

CIort.

0

~
.0

f)

.

~.:.

0

(%)

~_

,I (' .~"

I;c-""-

~'"

~~~~~:~

L

o~.,

t,·",,'v
).,
tv

~:

_ ..
MC11

__

MonmorioIt.

.••... KeoIini\e

...•..

CIoriI.

Fig. 7. Distribution of monmoriolite, kaolinite, illite and chlorite in sediments on tidal flats


176

BAo cAo KHOA HOC HOI THAo VAST - IRD V~ KHOA HOC BIt:N

Chlorite concentration was only higher than that of monmoriolite in clay minerals.
The concentration was higher at MC 5, MC 6 and lower in other cores. Comparison with
other clay minerals in tidal sediments, the concentration of chlorite was changed in
depths but not so clear.
Fenspate in sediments was high in concentration at MC 8 and MC 11 at depth
from 30cm to the end of cores. The lowest concentration of fenspate was at MC 2 and
MC 3, but not clearly changing in the cores.
NMLKJIHGFEDCBA

..~': "" .,:.--" " "

Cootentofminefilis

(%l

,

0
0

'''.

(

1"

'"

of minerals

Content

(%)

of minerals

("!o )

",

-,~J
MC>

",J
K

Content

eo

.
•

MC5

__

- •••.. Quatlz

-a··
Go.Ih~

\

1<::,~
/

K"
xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJ
F.n-,,"

Fenspat&

...~ .. Qu~
e-. Goe4i>M

L

-+..•..

•

QUlII1z

Go.IhiI •

~

Conlenlofminerals(%)

o

10~

~

~

~

ro ~

~

0r---~---"~'~'~'~~~

···•
•·.
·.:
·
"

~

"

~
.f

MC6

.

-.•...F,,"-, •
-.-

""""
Goelh.

~
o

o

-"
~

""

!"

l

ConlentofmineraJs

dcbaZYXWVUTSRQPONMLKJIHGFEDCBA
("to )

Fig. 8. Distribution of fenspate, quartz and goethite in sediments on tidal flats

Quartz in tidal sediments was quite high in concentration at all cores. In Table 4
standard deviation of mineral is high with quartz, this mineral are most abundant in tidal
sediment, if concentration of quartz changes that mean sedimentary environment are
changed, these event are shown in MC 3 (at 20-70 em in depth), MC 6 (at 30 - 40cm in
depth), MC 8 (27-40 em in depth) and MC 11 (27-50 em in depth) (fig. 8).
Goethite had the highest concentration at MC 2, followed by those at MC 5, MC
6. In the other cores, the change in concentration was not so high. As the results, it is
difficult to indicate for dynamic conditions, but it may be an indicator for physical chemical of sediment.


PROCEEDINGS

ON MARINE SCIENCExwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJI
177

OF VAST - IRD SYMPOSIUM

Generally, in three environments mentioned above, common clay minerals in
sediment cores are kaolinite and illite. The highest content in these clay minerals are in
the order: MC 5 > MC 6 > MC 7 > MC 8 > MC 11 > MC 2. Quartz was concentrated at
MC 3. Taking the concentrations of clay minerals and quartz as indicators for
sedimentary processes, the accretion takes place where high clay minerals are
concentrated and the erosion with low sedimentation rates is at the areas with high
quartz concentration.
Finally connection all data in sediment cores shows that used 210Pb and 226Ra in
monitoring sedimentation
rates only true for the accretion environment,
but
environmental erosion did not specify the exact age. This problem is seeing in sediment

cores at MC 3, MC 8, MC 9, and MC 11, other sediment parameters are complementary
to each other reflect sedimentary processes at tidal flats. As difference of21°Pb and 226Ra
at layers are causes of during time, mean diameters, clay minerals and condition
environment. All of them show clearly two sedimentary processes which are erosion and
accretion in the North of Vietnam.

5. CONCLUSION
Based on study results on the sedimentary characteristics
of grain size,
sedimentation rate, metals and minerals, three sedimentary environments are classified,
including deltaic tidal flat sedimentary environment from Kim Son to southwest Do Son
Peninsula, estuarine tidal flat sedimentary environment from northeast Do Don
Peninsula to southwest Cat Ba Island and embayment tidal flat sedimentary environment
from Cat Ba to Mong Cai.
In deltaic tidal flat sedimentary environment, two sedimentary processes of
accretion that is dominant and erosion that appears at 30cm in depth of MC 8, MC 9,
MC 10 and MC 11 are with common fine sediments and high sedimentation rate,
accumulation of metals in sediment, high clay minerals concentration. Estuarine tidal
flat sedimentary environment is characterised by accretion process, dominating fine
sediment, high sedimentation rate, highest accumulation of metals and high clay
minerals. Embayment tidal flat sedimentary environment is with low sedimentation rate,
common coarse sediments, low accumulation of metals and high quartz.
The study results from a large area with 11 sediment cores are initial information
on sedimentary environments. For future understanding the sedimentary processes in the
region, more studies and detail research plans should be developed and carried out.
These studies will contribute to use and manage tidal flats, function and fate of them in
local environmental conditions.dcbaZYXWVUTSRQPONMLKJIHGFEDCBA
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s u b s a m p lin g a n d h a n d lin g .

6. REFERENCES
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